Please Don’t Be Tired of This Data Yet (A Gila Monster Story)

I was lucky enough to already be using morphological data for my thesis project, so I decided to use the data I already had to kill 2 birds with one stone since I will be using some of these visualizations for my own project.

A T-Test

Here is my example of doing a T-test table and ggplot visualization for this exercise. Through my analysis you will see these same 9-10 morphological measurements that I collected for my thesis.

Table 1. Heloderma suspectum Morphological Characteristics
Female1 Male1 P-value2
SVL (mm) 265.2 (51.2) 239.5 (65.1) <0.001
Tail Length (mm) 124.0 (25.1) 111.9 (34.1) 0.004
Trunk 153.0 (34.5) 135.3 (40.4) <0.001
Tail Diameter (mm) 21.6 (6.2) 20.0 (7.2) 0.11
Insert to Elbow Length (mm) 16.8 (3.1) 16.0 (4.5) 0.29
Elbow to Wrist Length (mm) 21.6 (4.1) 20.7 (5.8) 0.45
Wrist to 3rd Digit Length (mm) 28.1 (4.8) 26.6 (6.9) 0.21
Head Length (mm) 45.1 (7.0) 42.6 (10.1) 0.14
Head Width (mm) 40.6 (7.7) 38.6 (11.4) 0.65
Ear to Rostral Length (mm) 50.5 (8.0) 47.7 (12.0) 0.35
1 Mean (SD)
2 Wilcoxon rank sum test

Here is a bar graph to act as a visualization for my T-test.

An ANOVA Analysis

Here is my ANOVA analysis for my data. For this section I chose to keep beaded lizard (Heloderma horridum) data in to allow for a between species comparison. As you can see, there is a large sample size difference between both the species and sexes.

Table 2. Heloderma species morphology
H. horridum H. suspectum P-value
Sex 0.018
    Female 25 138
    Male 20 232
SVL 310.7 (59.8) 248.5 (61.5) <0.001
Tail Length 223.1 (61.1) 113.9 (35.4) <0.001
Trunk 170.7 (36.1) 142.3 (38.7) <0.001
Tail Diameter 25.3 (6.4) 20.6 (7.0) <0.001
Insert to Elbow Length 22.3 (5.1) 16.4 (4.1) <0.001
Elbow to Wrist Length 28.9 (6.5) 21.1 (5.2) <0.001
Wrist to 3rd Digit Length 36.1 (6.8) 27.3 (6.2) <0.001
Head Length 52.3 (9.9) 43.7 (9.1) <0.001
Head Width 47.2 (11.4) 39.4 (10.1) <0.001
Ear to Rostral Length 58.4 (9.8) 48.8 (10.6) <0.001

Here is a visualization of one of the morphological measurements compared between species.

An ANCOVA Table

Here is an ANCOVA analysis done between sexes, including 9 of my morphological measurements after accounting for SVL. This is one of the types of analysis I will be using in my thesis.

Characteristic Female, N = 133 Male, N = 225 Adjusted Difference 95% CI1 p-value
Tail Length 124.0(25.1) 111.9(34.1) -0.48 -2.6, 1.6 0.7
Trunk 153.0(34.5) 135.3(40.4) 1.8 -0.20, 3.9 0.077
Tail Diameter 21.6(6.2) 20.0(7.2) -0.90 -1.7, -0.11 0.025
Insert to Elbow Length 16.8(3.1) 16.0(4.5) -0.70 -1.2, -0.24 0.003
Elbow to Wrist Length 21.6(4.1) 20.7(5.8) -1.1 -1.6, -0.53 <0.001
Wrist to 3rd Digit Length 28.1(4.8) 26.6(6.9) -0.99 -1.5, -0.51 <0.001
Head Length 45.1(7.0) 42.6(10.1) -1.2 -1.8, -0.59 <0.001
Head Width 40.6(7.7) 38.6(11.4) -2.1 -2.8, -1.3 <0.001
Ear to Rostral Length 50.5(8.0) 47.7(12.0) -1.6 -2.2, -1.1 <0.001
1 CI = Confidence Interval

The ANCOVA visualization focusing on trunk size.